In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention.
In mining and stone industries, it is in many cases important to fractionate crushed stone and gravel into fractions of stones with different sizes. In most cases, fractionating or screening is done by supplying an unfractionated stream of crushed stone or gravel to a vibrating screen provided with a screening deck including screening holes for allowing stones smaller than the screening holes to pass through the holes.
In present screening arrangements the efficiency of the screening on each screening deck in the screening arrangement is affected by the length of the traveling path of the material to be screened on each screening deck. As the material passes through the holes of one screening deck, gravity and the inclination of the screening deck together make the material fall onto the below-located screening deck further down on that below-located screening deck, making the traveling path on the below-located screening deck too short for the material to be screened properly.
To increase the efficiency of the screening the screening decks have been longer than in the previous screening arrangements providing a longer traveling path on each deck. Another method of improving the efficiency has been to arrange the feeding box, which supplies the screening arrangement with the material to be screened, to be located outside the screening arrangement, see e.g. FIG. 6.
However, many application locations have limited space, which is why the lengthening of the screening deck or the external feeding box are undesired solutions.